NOTES: All data-Trade levels reflect the mode of transportation as a shipment enters or exits a U.S. Customs port. Flows through individual ports are based on reported data collected from U.S. trade documents. Low-value shipments (imports less than $1,250 and exports less than $2,500) and intransit shipments are not included in trade data.

Air-Data for all airports are based on U.S. port classifications and include a low level (generally less than 2 percent to 3 percent of the total value) of small user-fee airports located in the same region. Air gateways not identified by airport name include major airports in that geographic area in addition to small regional airports. Because of U.S. Census Bureau nondisclosure regulations, data for some of the air gateways include courier operations. For example, data for New Orleans International Airport include FedEx air cargo activity in Memphis, TN.

SOURCES: Air and water-U.S. Department of Commerce, Census Bureau, Foreign Trade Division, special tabulation, April 2009. Land-U.S. Department of Transportation, Research and Innovative Technology Administration, Bureau of Transportation Statistics, Transborder Freight Data, as of April 2009.